This invention relates to an improved process and catalyst for the alkylation of an isoparaffin with an olefin-acting agent. Specifically, the invention relates to a hydrofluoric acid alkylation process which utilizes an acid catalyst containing a cationic or anionic surfactant component along with hydrofluoric acid to improve the solubility of an isoparaffin in the acid catalyst and thus allows the process to utilize a reduced amount of dangerous hydrofluoric acid containing catalyst while maintaining product quality.
Alkylation of isoparaffinic hydrocarbons, such as isobutane and isopentane, with olefinic hydrocarbons such as propylene, butylene and amylenes or with other olefin-acting agents such as C.sub.3 -C.sub.5 alkylhalides, etc., using mineral acids such as hydrogen fluoride is well known as a commercially important method for producing gasoline boiling range hydrocarbons. The C.sub.5 -C.sub.10 hydrocarbons typically produced in isoparaffin-olefin alkylation operations are termed "alkylate". Alkylate is particularly useful as a motor fuel blending stock. It possesses motor and research octane ratings high enough that it may be employed to improve overall octane ratings of available gasoline pools in order to provide motor fuels which comply with the requirements of modern automobile motors. High octane alkylate blending components are particularly important in producing motor fuels of sufficiently high octane since it is now mandatory to avoid use of alkyl lead antiknock compounds in gasoline. A continuing goal in the art is to provide an economically attractive and intrinsically safe acid-catalyzed alkylation process.
Maximizing alkylate octane while providing the safest possible process is a sometimes difficult feat. The goal of maximizing alkylate octane takes on new significance with the recent phaseout of alkyl lead antiknock compounds as blending agents for gasoline as mandated by government regulation. Additionally, the government and society in general are becoming increasingly aware and apprehesive about the manufacture, use, and disposal of toxic chemicals. Hydrofluoric acid poses a definite health and environmental risk as it is extremely corrosive and therefore a potential health hazard. The minimization of the use of hydrofluoric acid in an alkylation process is therefore quite desirable.
In commercial isoparaffin-olefin alkylation operations using acid catalysts, generally, isobutane is the isoparaffin used and propylene, butylene and amylenes or a mixture of these olefins, are used as the olefin-acting agent. Typically, the acid catalyst will comprise hydrogen fluoride. In conventional operations, the isoparaffin, olefin-acting agent and hydrogen fluoride catalyst are first contacted and thoroughly admixed in an alkylation reactor, forming a reaction mixture, or emulsion. After a relatively short time, the alkylation reaction is substantially complete and the reaction mixture is withdrawn from the alkylation reactor and is allowed to settle by gravity into immiscible hydrocarbon and catalyst phases in a settling vessel. The hydrogen fluoride catalyst phase thus separated is returned to the alkylation reactor for further catalytic use. The hydrocarbon phase separated in the settling operation is further processed, e.g., by fractionation, to recover an alkylate product and to separate unconsumed isoparaffin for recyckle to the alkylation reactor. The recovered alkylate product may then be added to the motor fuel octane pool as a blending component. It is, therefore, desirable that the alkylate product has as high a research octane number as possible.